Wire connector



R. A. ELM

WIRE CONNECTOR June 28, 1966 Filed April 8, 1963 INVENTOR. float-27 4 ELM BY United States Patent 3,258,733 WIRE CONNECTOR 1 Robert A. Elm, St. Paul, Minn, assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn, a corporation of Delaware Filed Apr. 8, 1%3, Ser. No. 271,354 3 Claims. (Cl. 339-98) This invention relates to connectors for joining insulated electrical wires, particularly at terminal blocks or strips, without preliminarily stripping the insulation. A typical use of terminal blocks lies in electrical wiring, e.g., in the wiring of machines or buildings. The blocks may be constructed in various sizes and types-integral and modular, for exampleand designed to accept various sizes of wire. Normally, several sets of conductors are joined at each block.

conventionally, Wire conductors are attached to terminal blocks by screw or other kinds of pressure fasteners, or by soldering, methods which have various limitations. This invention is intended to provide a terrnined block in which speedy, simple, lasting and low resistance connections betwen wires can be made without use of any special tools. Such connections are possible using a slotted connector, such as shown in US. Patent 3,012,219. In this arrangement one or more wire conductors are held on a surface and a connector or bridge member including at least one slotted conductive plate is forced onto the conductors. The plate pierces insulation on the conductors and enters into firm contact with the metal wires. The plate is thin and resilient so that the jaws defining the slots resiliently spread apart and exert compression on the wire. Connections made in this manner have been tested and found to have a very low resistance and to maintain their high conductivitiey through repeated mechanical stresses, temperature or pressure changes, exposure to moisture or the passage of electric current. Connections are made very simply; there is no need to strip insulation from the wire and the connector is quickly and directly applied in a single operation. The connector plate may be plurally slotted so that a single connector has the capacity of joining several wires in one simple movement. A further advantage of these slotted connectors is that they may be attached to a wire without severing the wire. Thus a wire conductor may be tapped quickly with no significant change in resistance.

As described in Patent No. 3,012,219, slotted connectors are normally inserted into a groove-like aperture in a base, the grooved surface of which provides support for a conductor. Removal of the connector at a later time from the aperture and from association with a wire conductor has not usually been contemplated. Where desired, such .as separation has been difiicult and required that the connector be grasped with pliers, or pried loose with a suitable pointed probe or lever. With connectors of small size, e.g., as used on small-diameter communications wires, the prior art practice has therefore been to remove and discard the connector and the connected wireterminals. With larger connectors such as are used with power conductors or the like and in permanent installations such as terminal blocks, and which because of their size and construction are intended for long use, means for permitting an easy withdrawal and reuse of the connector is needed.

The present invention satisfies this requirement, and provides a resilient slotted plate fastener or connector which is rapidly and conveniently applied and as easily removed, while producing a completely elfective nonloosening low resistance connection.

These advantageous properties are most conveniently secured, in accordance with the present invention, by supporting the insulated wires or wire-ends to be connected 3,258,733 Patented June 28, 1966 between opposed supporting surfaces in a base member, and forcing into conductive resilient contact with said wires a pair of slotted or furcate connector plates joined at their closed ends by a cross-plate centrally perforated with a keyhole-shaped opening. A screw member having a shaft portion of decreased diameter passes through said opening and engages .a correspondingly threaded bore in said base member, providing means for securing or removing the connector plates, all as will hereinafter be more explicity described in terms of illustrative but nonlimitative examples and in connection with the appended drawing, in which FIGURE 1 is a perspective view of a terminal block in use and including a plurality of wire-connector elements, of which one is illustrated in exploded form;

FIGURE 2 is a plan view of a connector element previous to its final shaping;

FIGURE 3 is a partial side elevation, partly in section, of a terminal block and wire connector, associated, but not finally assembled;

FIGURE 4 is a view of the structure of FIGURE 3 showing the connector in its assembled position;

FIGURE 5 is a section view taken the line 5-5 of FIGURE 3;

FIGURE 6 is a sectional view corresponding to that in FIGURE 5 showing another embodiment of the invention; and

FIGURE 7 is a perspective view of a terminal block showing a further embodiment of the invention.

The terminal block shown in FIGURES 1-5 comprises an insulating base 10 with flange 11 through which screws 12 attach the block to a supporting surface. Elevated barrier ribs 14 on the top surface of the base 10 serve as barriers against arcing betweeen adjoining connection. Between each two ribs the block 10 is grooved to provide two open-top, rectangular grooves or recesses 15 for receiving the legs of an inverted U-shaped connector member 17. A plurality of tubular, wire-receiving passages 16 extend through the base 1:) and pass perpendicularly through the walls of the slots 15; in the construction shown two such passages are provided for each pair of grooves and associated U-shaped connector.

The connector 17 is shown in FIGURE 2 in the form of a fiat blank or rectangular conductive plate member. The opposed ends are doubly slotted at 18, providing a plurality of fingers 23, the opposing edges of adjacent fingers being generally parallel while diverging near the ends of the fingers. The opposing parallel edges are separated by a distance somewhat less than the diameter of the smallest wire conductor to which connection is to be made. The connector plate blank is doubly folded as indicated by dotted lines to form the U-shaped connector shown most clearly in FIGURES 1 and 5, having legs 19 and a central portion 20. The central portion 20 is provided with a keyhole-shaped slot 21 having a circular larger portion 21a and a radially extended narrower portion 21b.

The legs 19 of the connector are so proportioned that, when in position in the openings 15 of the block, the slots 18 in the legs are above and in alignment with the passages 16. As the connector is forced into the opening, the ends of the fingers 23 come into contact with the wires 22 in the passages 16. Upon further insertion, the con ductors 22 enter the narrower portion of the slots 18 and the opposing edges of the fingers cut into and through any insulation 2211 around the metal wires 22b. The narrow edges of the fingers deform the metal wire as shown in FIGURE 4, and at the same time the fingers are resiliently spread apart from their original position. This spreading, however, is not sufiicient to overcome the elastic strain point of the metal. A connection results in which the fingers, attempting to spring back to their original position, exert a continued pressure against the wire. In order that the connector be received on the wire resiliently, the fingers 23 must not be externally restrained. Accordingly,the width of the slot must be sufficient to receive the leg 19 and still leave room for outward movement of the fingers. Connections made in this manner, as noted earlier, have been tested and found to provide unusually low resistance junctions that last through repeated mechanical stresses, and temperature and pressure changes.

The connectors are fastened to the block by screws 24 which pass through the aperture 21 in the connector. The screws are reduced in diameter at the neck 24a to form a shoulder 24b. The aperture 21 has an oversized part 21a as one means of facilitating reception of the screws; after the screws are inserted into the oversized part 21a, the neck is moved into the reduced part 2112. The width of the reduced part 21b of the keyhole is approximately the same as the diameter of the neck 24a and is less than the diameter of the shoulder 24b or the head of the screw. Cylindrical holes 25 in the block 10 are defined by a wall threaded to receive the screws. As the screws are tightened down, the connectors are forced onto the conductors. Thus connections are made very simply with ordinary tools.

Conductors can also be connected to the screws 24 by conventional means, such as Wrapping the bare end of a wire around the screw or inserting a spade type lug between the screw-head and the surface of the center plate 20, prior to tightening the screw, as illustrated in FIG-' URE 1. Connection at this point preferably is made after the connector has been forced over the conductors 22 by action of the screw 24. The reduced neck 24a on the screw permits it to be backed off, after the connector has been fully inserted into the openings and the electrical connection made, a distance sufficient to permit insertion of a spade terminal or bare Wire-end without disturbing the connection between the wires 22 and the connector 17.

When it is desired to disconnect, remove, or replace a conductor, the screw 24 is backed off until the shoulder 24b abuts the underside of the connector whereupon further removal of the screw lifts the connector up and eventually disengages it from the wire conductors. The conductors are held against movement by the top surfaces of the tubular passages 16. This feature permits slotted connectors of the type used in this terminal to be with drawn simply and quickly without damage to the resilient connector and without the use of special tools. Thus connections can easily be changed at the terminal block and the terminal blocks may be reused in different ap plications.

A U type, double-slotted connector has been illustrated. Single-slotted connectors are also useful; up to three slots may equally well be provided for applications requiring the same. Further, the connector may have one instead of two legs, with a right angle extension for a screw. In addition, the connector may have a tubular or other non-planar configuration. In such constructions, the tubular element slides within an annular recess, and has one or more slots in opposed sides of one end of the tube. Typically, the connector is made from a hard-temper metal such as Phosphor bronze or a beryllium-copper alloy.

The insulating base 10 is preferably molded from a thermoset phenolic, though thermoplastic and ceramics are also useful as insulating base materials. Conductive metallic or other materials are also useful, particularly for non-electrical applications such as in connectors for structural rods or cables. The base is made either, as an integral multi-connector unit or in modulator sections. The dotted lines 27 in FIGURE 1 showing typical division lines. In the modulator construction, blocks with a large number of terminals may be assembled. The connector in FIGURE 1 illustrates some of the ways in which connectors made according to this invention can be used.

Other illustrative embodiments of the invention are indicated. FIGURE 6 illustrates a terminal block in which the insulating base 30 is provided with opposed coaxial wire-receiving passageways 31, spaced apart at the center of the base by a barrier 32 of insulating material that separates the ends of the conductors 22 being connected. Preferably the blocks construction also permits its use in the conventional manner, a typical approach being to relieve the barrier at its juncture with the passageway so that it may be easily broken out. In FIGURE 7 a terminal block 35 or modular section of a terminal block (cooperating with sections of similar on other shape) is provided with horiozntal grooves 36 in the sides of the block or section which serve as wire-receiving passageways.

As a specific illustrative but non-limiting example of the practice of this invention, a terminal is constructed as follows: the terminal body, as illustrated in FIGURE 1 is molded from a thermoset phenolic resin, with four pairs of passages 16 and slots 15. The terminal body comprises a block having a height of 0.520" and a width of 0.875 to which are added barrier ribs 0.188 high and 0.062 thick which provide adequate protection in a terminal having a 600 v. rating. The diameter of the tubular passages 16 is 0.100" and those associated in pairs are spaced apart, center to center, a distance of 0.140". The grooves or slots 15 in the block are 0.045 thick and 0.400 wide and the adjacent edges of the block defining the slots are spaced apart 0.437". Connectors 17 are stamped from 0.040" thick phosphor bronze sheet, tensile strength 120,000 lbs./ sq. in., and have a width of 0.375" and an overall length of 1.361". The fiat sheet is folded at each side of the center section on a 0.031 radius to form parallel legs 0. 475 long spaced apart 0.437. The parallel slots 18 in the legs are 0.050" wide, 0.400" long, and the finger 23 between the slots is 0.090" wide. The corners at the ends of the fingers are curved about a 0.031 radius to form work receiving openings. The distance from the closed end of a slot to the end of the planar portion of the leg, i.e., the dimension A in FIGURE 5, which is important in determining the amount of compressive force exerted by the fingers on the Wire, is 0.044". The diameter of the circular portion 21a of the keyhole-shaped aperture 21 is 0.166 and the width of the extension 21b is 0.122". The screw 24, a No. 8-32, has a diameter including threads of 0.164" reduced to 0.110" in the neck portion. The overall length of the screw is 0.375" and the length of the reduced portion is 0.188. Connector elements 17 such as used in the terminal described and having a 0.050 slot, can be used with AWG wire gages 12-14.

What I claim is:v

1. A connector assembly comprising: a base having a linearly extended wire supporting surface and an opposed wire retaining surface parallel thereto for maintaining a said wire in a defined position, said base being narrowly deeply recessed across said supporting and retaining surfaces intermediate the ends thereof, the closely spaced surfaces of said base forming the walls of the recess being perpendicular to said supporting and retaining surfaces, and said base further being provided with a cylindrical opening having a threaded wall parallel and adjacent to said recess; a conductive resilient connector member including a thin deeply slotted connector plate slidably fitting without constriction between said closely spaced surfaces with its large surface area sides closely adjacent the closely spaced surfaces for insertion past said supporting and retaining surfaces and with the slot in said plate in line with a wire supported on said supporting surface, the narrow edges defining said slot being generally parallel and including gradually diverging portions defining a wire accepting opening, said plate being further adapted for receiving a said wire under pressure sufficient to cause resilient separation of said narrow edges, said connector member further including a short apertured flat plate segment extending perpendicularly from the edge of said slotted plate opposite the wire accepting opening and with the aperture in line with said cylindrical opening; and a screw member having a threaded terminal portion cooperatively fitting within said cylindrical opening, a torque accepting head portion, and an intermediate neck portion of reduced diameter passing through the aperture in said connector plate segment and having a length at least equal to the combined thickness of said flat plate segment and a wire conductor to be contacted by said screw member, the head and threaded terminal portions having a diameter larger than the apertures width.

2. A connector assembly adapted for removably providing secure mechanical and electrical connection to insulated wires, comprising: a base having parallel side by side through-extending wire-receiving tubular passageways, providing wire supporting surfaces and opposed wire retaining surfaces for maintaining said wires in defined positions, said base being doubly narrowly deeply recessed across said passageways and said surfaces intermediate the ends thereof, the closely spaced parallel surfaces of said base forming the walls of a recess being perpendicular to the passageways and the supporting and retaining surfaces, and the recesses being spaced apart and parallel to one another, and said base being further provided with a cylindrical opening having a threaded wall parallel to and between said recesses; a wide conductive resilient U shaped connector member, each leg of the U being a thin wide plurally deeply slotted plate, one plate slidably fitting without constriction between each pair of said parallel surfaces with its fiat sides closely adjacent said surfaces for insertion past said passageways and supporting and retaining surfaces, and with a slot in each of said plates in line with a wire supported in a corresponding passageway, the narrow edges defining said slots being generally parallel and including gradually diverging portions defining wire accepting openings, said plates being further adapted for receiving a said wire in each slot under pressure sufficient to cause resilient separation of said narrow edges, the flat plate segment of the U connecting the legs including a central aperture in line with said cylindrical opening; and a screw member having a threaded terminal portion cooperatively fitting within said cylindrical opening, a torque accepting head portion, and an intermediate neck portion of reduced diameter passing through the aperture in said connector plate segment, the aperture having a narrow part in line with the cylindrical opening of sufficient diameter to receive the intermediate neck of reduced diameter but insufficient to permit passage of the threaded portion or head and a larger part adjacent and connected to the narrow part of a diameter sufiicient to receive the threaded portion, the head and threaded terminal portions having a diameter larger than the apertures width, causing said head and threaded terminal portions to engage the plate segment during movement of the screw to advance the connector member into, or withdraw it from the base.

3. A connector comprising: a base having a plurality of parallel wire-supporting and opposed wire-retaining surfaces and being narrowly deeply recessed across said surfaces intermediate the ends thereof, the closely spaced surfaces of said base forming the walls of the recess being perpendicular to said surfaces and said base being further provided with a cylindrical opening having a threaded wall parallel and adjacent to said recess; a conductive resilient connector member including a thin plurally deeply slotted connector plate slidably fitting without constriction between said closely spaced surfaces with its large surface area sides closely adjacent the closely spaced surfaces for insertion past said supporting and retaining surfaces and with the slots in said plate in line with wires supported on the corresponding wireretaining surfaces, the narrow edges defining each of said slots being generally parallel and including gradually diverging portions defining wire-accepting openings, said plate being further adapted for receiving a wire in each of said slots under pressure sufiicient to cause resilient separation of said narrow edges, and said connector member further including a short apertured flat plate segment extending perpendicularly from the edge of said slotted plate opposite the wire-accepting openings; and a screw member having a threaded terminal portion cooperatively fitting within said cylindrical opening, a torque-accepting head portion, and an intermediate neck portion of reduced diameter passing through the aperture in said connector plate segment, the aperture having a narrow part in line with the cylindrical opening and of sufficient diameter to receive the intermediate neck but insufficient to permit passage of the threaded portion or the head of said screw member, and being widened at one end to a diameter sufiicient to receive the threaded portion, the diameter of said threaded portion and of said head being greater than the width of said narrow part of said aperture.

References Cited by the Examiner UNITED STATES PATENTS 2,372,653 4/1945 Becket 33997 2,518,489 8/1950 Orlando 33997 2,628,263 2/1953 Bulla 339151 3,012,219 12/1961 Levin et al. 33998 3,118,715 1/1964 Potruch 33998 3,121,599 2/1964 Modray 339-189 X 3,177,456 4/1965 Haydu et al 339246 X PATRICK A. CLIFFORD, Primary Examiner. W. DONALD MILLER, Examiner. 

3. A CONNECTOR COMPRISING: A BASE HAVING A PLURALITY OF PARALLEL WIRE-SUPPORTING AND OPPOSED WIRE-RETAINING SURFACES AND BEING NARROWLY DEEPLY RECESSED ACROSS SAID SURFACES INTERMEDIATE THE ENDS THEREOF, THE CLOSELY SPACED SURFACES OF SAID BASE FORMING THE WALLS OF THE RECESS BEING PREPENDICULAR TO SAID SURFACES AND SAID BASE BEING FURTHER PROVIDED WITH A CYLINDERICAL OPENING HAVING A THREADED WALL PARALLEL AND ADJACENT TO SAID RECESS; A CONDUCTIVE RESILIENT CONNECTOR MEMBER INCLUDING A THIN PLURALLY DEEPLY SLOOTED CONNECTOR PLATE SLIDABLY FITTING WITHOUT CONSTRUCTION BETWEEN SAID CLOSELY SPACED SURFACES WITH ITS LARGE SURFACE AREA SIDES CLOSELY ADJACENT THE CLOSELY SPACED SURFACES FOR INSERTION PAST SAID SUPPORTING AND RETAINING SURFACES AND WITH THE SLOTS IN SAID PLATE IN LINE WITH WIRES SUPPORTED ON THE CORRESPONDING WIRERETAINING SURFACES, THE NARROW EDGES DEFINING EACH OF SAID SLOTS BEING GENERALLY PARALLEL AND INCLUDING GRADUALLY DIVERGING PORTIONS DEFINING WIRE-ACCEPTING OPENINGS, SAID PLATE BEING FURTHER ADAPTED FOR RECEIVING A WIRE IN EACH OF SAID SLOTS UNDER PRESSURE SUFFICIENT TO CAUSE RESILIENT 